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An ongoing two-year research is performing with the general objective to assess the feasibility of a system integrating the production of green-energy and its consumption inside and close to port areas for mobility services. The system is composed by two elements: (a) a “sea-to-grid” technological component harvesting and producing electrical energy from sea waves; and (b) a “green” logistic service based on the use of Fully Electric Vehicles (FEVs). A pilot study will be conducted near an Italian port area supporting passengers and freight mobility between a port and a backward (sub)-urban area. The proposed system is within the environmental goals set by the EU (Europe 2020 Strategy) and the Italian Government (National Energy Masterplan). Indeed, the energy-producing technology reduces dependence from traditional energy sources (coal, gas, oil) and consequently reduces their negative effects (greenhouse gases, air pollution, etc.). Considering that the energy is produced by sea waves, the system transfers the entire amount of produced (green) energy to the electric vehicles. The system will be experimented in a medium size urbanized area and the energy will be produced in a small size port.

The REWEC3 (Resonant Wave Energy Converter) is a fixed oscillating water column (OWC) wave energy converter (WEC) incorporated in upright breakwaters. The device is composed by a chamber containing a water column in its lower part and an air pocket in its upper part. The air pocket is connected to the atmosphere via a duct hosting a self-rectifying air turbine. In addition, a REWEC3 includes a vertical U-shaped duct for connecting the water column to the open sea (for this reason it is known also as U-OWC). The working principle of the system is quite simple: by the action of the incident waves, the water inside the U-shaped duct is subject to a reciprocating motion, which induces alternately a compression and an expansion of the air pocket. The pressure difference between the air pocket and the atmosphere is used to drive an air turbine coupled to an off-the-shelf electrical generator connected to the grid. The main feature of the REWEC3 is the possibility of tuning the natural period of the water column in order to match a desired wave period through the size of the U-duct. The REWEC3 technology has been theoretically developed by Boccotti, later tested at the natural basin of the Natural Ocean Engineering Laboratory (NOEL, Italy), and finally proved at full scale with REWEC3 prototype built in the Port of Civitavecchia (Rome, Italy). The objective of this paper is to select and optimize a turbine/generator set of a U-shaped OWC installed in breakwaters located in the Mediterranean Sea, such as the Port of Civitavecchia, where the first prototype of REWEC3 has been realized, or the Port of Salerno or Marina delle Grazie of Roccella (Italy). The computations were performed using a time domain model based on the unsteady Bernoulli equation. Based on the time-domain model of the power plant, the following data is computed for the turbines: i) the ideal turbine diameter; ii) the generator feedback control law aiming to maximize the turbine power output for turbine coupled to the REWEC3 device for Mediterranean applications.

The design of any wave energy converter involves the determination of relevant statistical data on the wave energy resource oriented to the evaluation of the structural reliability and energy performance of the device. Currently, limited discussions concern the estimation of parameters connected to the energy performance of a device. Thus, this paper proposes a methodology for determining average downtime and average missed energy, which is the energy that is not harvested because of device deactivations during severe sea storms. These quantities are fundamental for evaluating the expected inactivity of a device during a year or during its lifetime and are relevant for assessing the effectiveness of a device working at a certain site. For this purpose, the equivalent power storm method is used for their derivation, starting from concepts pertaining to long-term statistical analysis. The paper shows that the proposed solutions provide reliable estimations via comparison with results obtained by processing long wave data.

The Resonant Wave Energy Converter 3 (REWEC3) is a wave energy converter belonging to the family of Oscillating Water Columns (OWCs). It comprises an oscillating water column and an air pocket connected to a turbine, as for traditional OWCs. In addition, it has a small vertical U-shaped duct used for connecting the water column to the open wave field. Because of this particular geometrical configuration, it is also known as U-Oscillating Water Column (U-OWC). During the past decade, small scale field experiments and theoretical analyses proved its potential for full scale applications. Currently, a full-scale prototype has been operating in the Port of Civitavecchia (Rome, Italy), where a REWEC3 was constructed within the context of a major port enlargement. This paper shows some results of the monitoring activity on a single chamber equipped with pressure gauges. The results show some initial energetic performances of the REWEC3 in wind-generated seas.

The design of an energy harvester involves achieving the two following objectives: to install a safe structure with a reasonable safety margin; and to install an effective device which is able to capture energy in a variety of environmental conditions. In this context, the long-term modelling of the environmental variables plays a crucial role. In the context of wave energy harvesters, the occurrence of sea storms is a critical element in the design process. Indeed, its identification is required for determining extreme loads as well as controlled de-activations of the device for preserving the mechanical components into the device. Considering these issues, the paper proposes an analysis of the wave climate oriented to the determination of the downtime and of the energy losses. Specifically, the paper provides expressions: for calculating the average deactivation time of a wave energy device, given that it must be deactivated if the significant wave height is larger than a certain threshold; and for calculating the energy “lost” (as it is not absorbed by the device) during a storm in which the maximum wave height is larger than the mentioned threshold. The paper shows that closed-form expressions can be obtained by relying on the Equivalent Triangular Storm (ETS) model and that the adequacy of the estimations improves for larger values of the significant wave height threshold.

This paper deals with the implementation of a control algorithm for a turbine equipped into a U-Oscillating water column (U-OWC) plant. The open literature has largely ignored the problem of coupling the U-OWC behaviour to the turbine behaviour with the objective of maximizing the energy harvesting. Therefore, this paper has the objective of assessing the reliability of a Maximum Power Point Tracking (MPPT) algorithm. The paper uses a numerical algorithm for estimating the energy produced by a U-OWC in real seas. In this regard, the computations rely on long time domain analyses that allow testing a variety of environmental conditions. The MPPT is proved adequate for controlling the turbine behavior in conjunction with U-OWCs. In this context, it is shown that a reference parameter, used for determining the reference rotational speed, can be the significant wave height.

The objective of this paper is to provide a synthetic tool for determining expeditiously the wave climate conditions in several areas of the Mediterranean Sea. In the open literature, several authors have already conducted this specific analysis also for the area under examination in this paper. However, the need of discussing aspects strictly related to the design of wave energy harvesters is still relevant. Therefore, considering the variety of devices and the amount of information needed for conducting both an energy-wise optimization and a structural reliability assessment, a holistic view on the topic is provided. Specifically, the paper elucidates the theoretical aspects involved in the estimation of wave energy statistics and in the calculation of relevant return values. Next, it provides synthetic data representing the mean wave power and the return value of extreme events in several coastal areas of the Mediterranean Sea. In this regard, the paper complements information available in the open literature by discussing the influence of the directional pattern of the sea states in the determination of sea state statistics as well as in the design of a wave energy harvester. © 2014 Elsevier Ltd.

Since the nineties, the OWC (Oscillating Water Column) plants were developed at full scale to produce electrical power from ocean waves [1]. A prototype was built into a caisson breakwater of the Sakata Port, in Japan; other plants were built in India, in Scotland at Islay, in Portugal at the Azores. A new plant was built in Mutriku (Spain) recently. A new kind of OWC caisson, named U-OWC or REWEC3, was proposed by Boccotti [2]. With respect to a traditional OWC, a U-OWC plant includes an additional vertical duct, which enables to tune the eigenperiod of the plant to the peak period of the wave pressures acting on the converter-breakwater. In this way, resonance conditions can be reached without phase control devices and the wave pressures into the air pocket are increased in amplitude, amplifying the performance of the plant. In 2012, a full scale U-OWC (REWEC3) breakwater has been designed in Italy, for the harbour of Civitavecchia (the port of Rome – Port Authority of Civitavecchia). Such a breakwater embodies 19 caissons, each including 8 cells, 34m long. The paper disseminates the key issues pertaining the design stage. Further, it describes the main phases of the construction stage. The building of the caisson started in October 2012. The first caisson has been completed at the end of 2012. It is the first device for wave energy in the Mediterranean Sea and one of the biggest in the world.Copyright © 2013 by ASME

In the last decades, the research has directed its efforts and resources paper is to investigate towards the possibility to incorporate wave energy converters, into the traditional maritime breakwaters to combine classical use with new opportunities and developments (for example, the Green Ports). Since the nineties, the OWC (Oscillating Water Column) plants were developed at full scale to produce electrical power from ocean waves. For instance, a new plant was built in Mutriku (Spain) recently. A new kind of OWC caisson, named U-OWC or REWEC3, which has the advantage to obtain an impressive natural resonance without any device for phase control, has been patented by Boccotti [1]. This new U-OWC device gives performances better than those of a conventional OWC either with small wind waves or with high waves [2,3,4]. The properties of the REWEC3 have been verified with two small-scale field experiments carried out in the natural ocean engineering laboratory NOEL of Reggio Calabria off the eastern coast of the Sicily Channel [5–7]. The aim of the present two sites along Italian coasts for possible installations of REWEC3 devices: i) the port of Civitavecchia (Rome, Italy)in the Tyrrhenian sea; ii) the port of Pantelleria, in the Sicily Channel.

This paper deals with the random forces produced by high ocean waves on submerged horizontal circular cylinders. Arena [Arena F, Interaction between long-crested random waves and a submerged horizontal cylinder. Phys Fluids 2006;18(7):1–9 (paper 076602)] obtained the analytical solution of the random wave field for two dimensional waves by extending the classical Ogilvie solution [Ogilvie TF, First- and second-order forces on a cylinder submerged under a free surface. J Fluid Mech 1963;16:451–472; Arena F, Note on a paper by Ogilvie: The interaction between waves and a submerged horizontal cylinder. J Fluid Mech 1999;394:355–356] to the case of random waves. In this paper, the wave force acting on the cylinder is investigated and the Froude Krylov force [Sarpkaya T, Isaacson M, Mechanics of wave forces on offshore structures, Van Nostrand Reinhold Co.; 1981], on the ideal water cylinder, is calculated from the random incident wave field. Both forces represent a Gaussian random process of time. The diffraction coefficient of the wave force is obtained as quotient between the standard deviations of the force on the solid cylinder and of the Froude Krylov force. It is found that the diffraction coefficient of the horizontal force C d o is equal to the C d v of the vertical force. Finally, it is shown that, since a very large wave force occurs on the cylinder, it may be calculated, in time domain, starting from the Froude Krylov force. It is then shown that this result is due to the fact that the frequency spectrum of the force acting on the cylinder is nearly identical to that of the Froude–Krylov force.

The upright fully reflective wall-types breakwaters have been widely adopted for development of harbours. The design of these structures depends on the characteristic wave field resulting from the interaction of the sea waves with the reflective structure, which is strongly irregular and nonlinear. This paper deals with the mechanics of long-crested wave groups in front of a vertical wall. For this purpose the ‘Quasi Determinism’ theory, particularized for the reflection of sea wave groups, is extended up to the second-order. The nonlinear processes free surface displacement and velocity potential, when a large wave crest occurs on the vertical wall or in front of it, are obtained. In the application some properties of nonlinear wave groups in reflection, when a high wave crest occurs on the wall or in front of it, are investigated.Copyright © 2007 by ASME